For the Greek gov't to rebalance its primary deficit from negative five percent of GDP, then the Greek gov't would need to withdraw spending to the tune of five percentage points of GDP times the tax rate and divided by the money savings rate of the people from whom it is withdrawn. So more like 15 % of Greek GDP, or around half of the government's budget.

Keynesian multipliers are just as dramatic in reverse as they are when you're doing it right...